The president's attendance, which was uncertain because of a recent U.S. arms sale to Taiwan, could boost President Obama's efforts to curb Iran's and North Korea's nuclear programs.

Reporting from Beirut and Beijing — China announced Thursday that President Hu Jintao planned to attend a nuclear nonproliferation conference this month in Washington, an affirmative gesture after months of giving the cold shoulder to the Obama administration over a U.S. arms sale to Taiwan.

Hu's attendance at the conference, a major initiative of President Obama, also could help the United States and China coordinate a united stance in pressuring Iran and North Korea to abandon their nuclear ambitions.

Susan E. Rice, U.S. ambassador to the United Nations, had said Wednesday that China would join talks in New York with the United States, Britain, France, Russia and Germany about how to draft tighter economic sanctions against Iran, which has been subject to three rounds of sanctions since 2006.

U.S. officials said Thursday that they were pleased to hear that Hu would take part in the Washington conference.

"We welcome his decision," said Philip Crowley, the chief State Department spokesman.

He said China's participation "at the highest possible level" was a sign of the country's interest in nuclear security. Iran says its nuclear program is meant to generate power for civilian use, but many in the international community believe its goal is to develop nuclear weaponry.

Also Thursday, Iran's top nuclear negotiator, Saeed Jalili, arrived in Beijing, where he was expected to meet with Foreign Minister Yang Jiechi and State Councilor Dai Bingguo.

"The Islamic Republic of Iran and China are two countries with diverse political, economic and international potentials," Jalili said, according to state radio in Tehran. "There are good ties between us and China. . . . I came here in order to consult on certain issues which are of interest to both parties."

Chinese Foreign Ministry spokesman Qin Gang told reporters at a briefing in Beijing that Hu would stop in Washington on April 12 and 13 on his way to visit Brazil.

"The nuclear security summit will mainly discuss the threat posed by nuclear terrorism," Qin said. He was cautious when pressed on Beijing's Iran policy, saying only that "China will continue to endeavor toward a peaceful resolution."

Yin Gang, a Middle East expert at the Chinese Academy of Social Sciences, said Chinese officials were expected to press the visiting Iranian envoy on his country's nuclear ambitions.

"The Iranians have disappointed China time after time with their nuclear program," Yin said. "If Iran continues with its nuclear program in this manner, they should not expect China to acquiesce."

As Western countries have reduced their trade with Iran, China has stepped up to fill the void. About 14% of China's imported oil comes from Iran and the two countries engaged in $27 billion worth of trade in 2008.

Jin Liangxiang of the Shanghai Institute for International Studies said China nevertheless would have limited powers of persuasion with the Iranians.

"China has very good political and economic relations with Iran," Jin said, "but Iran is very independent-minded."

Iran does not fear that China will sacrifice its energy security and strategic partnership with the Islamic Republic by endorsing biting sanctions to appease Iran's Western rivals, analysts say. But it does worry that China could be enticed to endorse watered-down sanctions, which weaken Tehran's diplomatic position without harming its economy.

"Iran is concerned that China's resistance may be whittled down by various diplomatic efforts which might entail some carrots," said Kaveh Afrasiabi, a former advisor to Iran's nuclear negotiating team who is now a Cambridge, Mass.-based scholar. "They're concerned about any potential bargaining between the U.S. and China."

The Iranian government is striving to counter the diplomatic offensive against it by the West, headed by a politically rejuvenated Obama. Tehran will host a nuclear disarmament conference coinciding with Obama's nonproliferation gathering in Washington.

"Naturally Iran is putting its diplomatic machinery into higher gear vis-a-vis all the diplomatic efforts against it by the U.S. coalition," Afrasiabi said. "The dispatch of a diplomat to Beijing makes perfect sense to ward off any negative influence by the U.S. on China."

Analyst Jin predicted, however, that Beijing might be able to score some points with North Korea. Intelligence officials in South Korea have said that North Korean leader Kim Jong Il probably would visit China soon and that the Chinese might offer him a much-needed infusion of aid in exchange for the country's return to multinational talks on denuclearization.

The coming Global Nuclear Security Summit is a key initiative by Obama to rally international support in the fight against nuclear terrorism. More than 40 heads of state have been invited. Whether China's president would attend had been a subject of much consternation in Washington, with Beijing giving few clues to its intentions.

Obama promised during his presidential campaign that he would take steps to reduce the threat of nuclear terrorism, and attendance at the gathering is a matter of personal prestige on what he views as a core foreign policy issue. U.S. officials said they had emphasized to the Chinese the strong desire for Beijing to have high-level representation.

China had announced in late January that it was suspending security exchanges with the United States over the $6.4-billion arms sale to Taiwan. Relations also have been frayed by Obama's meeting in February with the Dalai Lama, the Tibetan spiritual leader; by U.S. demands for China to revalue its currency; and by the flap over Internet censorship.